Polyamines are naturally occurring, major ionic constituents that interact with DNA in virus, bacteriophage and all cells. Counterion condensation of DNA in vitro produces, virus sized torus shaped structures. Our observations support a unidirectional, circumferential wrapping model for DNA organization in toruses and document specific ion effects on DNA condensate stability. Our specific aims are to use biochemical and electron microscopic approaches to test the unidirectional, circumferential wrap model of torus organization by varying the size of linear and circular DNAs. The effect of specific ions, including (NH3)5Ru3+-DNA, and dehydrating protocols versus the hydrating freeze-etch technique on condensed particle distribution will be examined. Our data suggest a thin, disk shaped torus having lower limit dimensions predicted by the thermo theory of Manning. We intend to test these ideas by measuring torus population dimensions from a variety of DNA types and condensing ions with large tilt angle stereomicrograph series to get end-on views and direct thickness measurements. Our pH dependent specific ion effects, differentiating between various polyamines and inorganic cations, will be tested to see if aggregation and methylene bridging capacity are responsible for this effect. During our studies of DNA toruses we developed a methodology to accurately measure DNA tertiary structure writhe using stereometer measurements on paired stereomicrographs from freeze fracture, deep-etched replicas. Using this mature methodology, we aim to make shape and DNA topological descriptions in the following two very important chromosomal systems-nucleosome crystals to complement their current x-ray study and internal DNA organization in P22 and T7 bacteriophage to complement their drug binding structure investigations. We hope to be able to help decide between two conflicting models of nucleosome structure based on different x-ray studies (Uberbacher/Klug vs. Moudrianakis/Burlingame) if we are successful in visualizing DNA pitch and pitch angle on surface nucleosomes of microcrystals as well as identifying any possible nucleosome structure polymorphism. In bacteriophage we hope to be able to identify the major DNA organization of bacteriophage interiors. This study will help elucidate the mechanism of DNA packaging, a problem of considerable interest and one not well understood.